Remove diagnostic dependent output in structuredTypeRelatedTo

src/compiler/checker.ts

@@ -12570,6 +12570,7 @@ namespace ts {
 
                 let result: Ternary;
                 let originalErrorInfo: DiagnosticMessageChain | undefined;
+                let varianceCheckFailed = false;
                 const saveErrorInfo = errorInfo;
 
                 // We limit alias variance probing to only object and conditional types since their alias behavior
@@ -12579,11 +12580,10 @@ namespace ts {
                     source.aliasTypeArguments && source.aliasSymbol === target.aliasSymbol &&
                     !(source.aliasTypeArgumentsContainsMarker || target.aliasTypeArgumentsContainsMarker)) {
                     const variances = getAliasVariances(source.aliasSymbol);
-                    if (result = typeArgumentsRelatedTo(source.aliasTypeArguments, target.aliasTypeArguments, variances, reportErrors)) {
-                        return result;
+                    const varianceResult = relateVariances(source.aliasTypeArguments, target.aliasTypeArguments, variances);
+                    if (varianceResult !== undefined) {
+                        return varianceResult;
                     }
-                    originalErrorInfo = errorInfo;
-                    errorInfo = saveErrorInfo;
                 }
 
                 if (target.flags & TypeFlags.TypeParameter) {
@@ -12747,31 +12747,9 @@ namespace ts {
                         // type references (which are intended by be compared structurally). Obtain the variance
                         // information for the type parameters and relate the type arguments accordingly.
                         const variances = getVariances((<TypeReference>source).target);
-                        if (result = typeArgumentsRelatedTo((<TypeReference>source).typeArguments, (<TypeReference>target).typeArguments, variances, reportErrors)) {
-                            return result;
-                        }
-                        // The type arguments did not relate appropriately, but it may be because we have no variance
-                        // information (in which case typeArgumentsRelatedTo defaulted to covariance for all type
-                        // arguments). It might also be the case that the target type has a 'void' type argument for
-                        // a covariant type parameter that is only used in return positions within the generic type
-                        // (in which case any type argument is permitted on the source side). In those cases we proceed
-                        // with a structural comparison. Otherwise, we know for certain the instantiations aren't
-                        // related and we can return here.
-                        if (variances !== emptyArray && !hasCovariantVoidArgument(<TypeReference>target, variances)) {
-                            // In some cases generic types that are covariant in regular type checking mode become
-                            // invariant in --strictFunctionTypes mode because one or more type parameters are used in
-                            // both co- and contravariant positions. In order to make it easier to diagnose *why* such
-                            // types are invariant, if any of the type parameters are invariant we reset the reported
-                            // errors and instead force a structural comparison (which will include elaborations that
-                            // reveal the reason).
-                            if (!(reportErrors && some(variances, v => v === Variance.Invariant))) {
-                                return Ternary.False;
-                            }
-                            // We remember the original error information so we can restore it in case the structural
-                            // comparison unexpectedly succeeds. This can happen when the structural comparison result
-                            // is a Ternary.Maybe for example caused by the recursion depth limiter.
-                            originalErrorInfo = errorInfo;
-                            errorInfo = saveErrorInfo;
+                        const varianceResult = relateVariances((<TypeReference>source).typeArguments, (<TypeReference>target).typeArguments, variances);
+                        if (varianceResult !== undefined) {
+                            return varianceResult;
                         }
                     }
                     else if (isReadonlyArrayType(target) ? isArrayType(source) || isTupleType(source) : isArrayType(target) && isTupleType(source) && !source.target.readonly) {
@@ -12798,16 +12776,48 @@ namespace ts {
                                 }
                             }
                         }
-                        if (result) {
-                            if (!originalErrorInfo) {
-                                errorInfo = saveErrorInfo;
-                                return result;
-                            }
-                            errorInfo = originalErrorInfo;
+                        if (varianceCheckFailed && result) {
+                            errorInfo = originalErrorInfo || errorInfo || saveErrorInfo; // Use variance error (there is no structural one) and return false
+                        }
+                        else if (result) {
+                            return result;
                         }
                     }
                 }
                 return Ternary.False;
+
+                function relateVariances(sourceTypeArguments: ReadonlyArray<Type> | undefined, targetTypeArguments: ReadonlyArray<Type> | undefined, variances: Variance[]) {
+                    if (result = typeArgumentsRelatedTo(sourceTypeArguments, targetTypeArguments, variances, reportErrors)) {
+                        return result;
+                    }
+                    const isCovariantVoid = targetTypeArguments && hasCovariantVoidArgument(targetTypeArguments, variances);
+                    varianceCheckFailed = !isCovariantVoid;
+                    // The type arguments did not relate appropriately, but it may be because we have no variance
+                    // information (in which case typeArgumentsRelatedTo defaulted to covariance for all type
+                    // arguments). It might also be the case that the target type has a 'void' type argument for
+                    // a covariant type parameter that is only used in return positions within the generic type
+                    // (in which case any type argument is permitted on the source side). In those cases we proceed
+                    // with a structural comparison. Otherwise, we know for certain the instantiations aren't
+                    // related and we can return here.
+                    if (variances !== emptyArray && !isCovariantVoid) {
+                        // In some cases generic types that are covariant in regular type checking mode become
+                        // invariant in --strictFunctionTypes mode because one or more type parameters are used in
+                        // both co- and contravariant positions. In order to make it easier to diagnose *why* such
+                        // types are invariant, if any of the type parameters are invariant we reset the reported
+                        // errors and instead force a structural comparison (which will include elaborations that
+                        // reveal the reason).
+                        // We can switch on `reportErrors` here, since varianceCheckFailed guarantees we return `False`,
+                        // we can return `False` early here to skip calculating the structural error message we don't need.
+                        if (varianceCheckFailed && !(reportErrors && some(variances, v => v === Variance.Invariant))) {
+                            return Ternary.False;
+                        }
+                        // We remember the original error information so we can restore it in case the structural
+                        // comparison unexpectedly succeeds. This can happen when the structural comparison result
+                        // is a Ternary.Maybe for example caused by the recursion depth limiter.
+                        originalErrorInfo = errorInfo;
+                        errorInfo = saveErrorInfo;
+                    }
+                }
             }
 
             // A type [P in S]: X is related to a type [Q in T]: Y if T is related to S and X' is
@@ -13316,17 +13326,17 @@ namespace ts {
 
         function getVariances(type: GenericType): Variance[] {
             // Arrays and tuples are known to be covariant, no need to spend time computing this (emptyArray implies covariance for all parameters)
-            if (!strictFunctionTypes || type === globalArrayType || type === globalReadonlyArrayType || type.objectFlags & ObjectFlags.Tuple) {
+            if (type === globalArrayType || type === globalReadonlyArrayType || type.objectFlags & ObjectFlags.Tuple) {
                 return emptyArray;
             }
             return getVariancesWorker(type.typeParameters, type, getMarkerTypeReference);
         }
 
         // Return true if the given type reference has a 'void' type argument for a covariant type parameter.
         // See comment at call in recursiveTypeRelatedTo for when this case matters.
-        function hasCovariantVoidArgument(type: TypeReference, variances: Variance[]): boolean {
+        function hasCovariantVoidArgument(typeArguments: ReadonlyArray<Type>, variances: Variance[]): boolean {
             for (let i = 0; i < variances.length; i++) {
-                if (variances[i] === Variance.Covariant && type.typeArguments![i].flags & TypeFlags.Void) {
+                if (variances[i] === Variance.Covariant && typeArguments[i].flags & TypeFlags.Void) {
                     return true;
                 }
             }

tests/baselines/reference/checkInfiniteExpansionTermination.errors.txt

@@ -0,0 +1,32 @@
+tests/cases/compiler/checkInfiniteExpansionTermination.ts(16,1): error TS2322: Type 'ISubject<Bar>' is not assignable to type 'IObservable<Foo>'.
+  Types of property 'n' are incompatible.
+    Type 'IObservable<Bar[]>' is not assignable to type 'IObservable<Foo[]>'.
+      Type 'Bar[]' is not assignable to type 'Foo[]'.
+        Property 'x' is missing in type 'Bar' but required in type 'Foo'.
+
+
+==== tests/cases/compiler/checkInfiniteExpansionTermination.ts (1 errors) ====
+    // Regression test for #1002
+    // Before fix this code would cause infinite loop
+
+    interface IObservable<T> {
+        n: IObservable<T[]>; // Needed, must be T[]
+    }
+
+    // Needed
+    interface ISubject<T> extends IObservable<T> { }
+
+    interface Foo { x }
+    interface Bar { y }
+
+    var values: IObservable<Foo>;
+    var values2: ISubject<Bar>;
+    values = values2;
+    ~~~~~~
+!!! error TS2322: Type 'ISubject<Bar>' is not assignable to type 'IObservable<Foo>'.
+!!! error TS2322:   Types of property 'n' are incompatible.
+!!! error TS2322:     Type 'IObservable<Bar[]>' is not assignable to type 'IObservable<Foo[]>'.
+!!! error TS2322:       Type 'Bar[]' is not assignable to type 'Foo[]'.
+!!! error TS2322:         Property 'x' is missing in type 'Bar' but required in type 'Foo'.
+!!! related TS2728 tests/cases/compiler/checkInfiniteExpansionTermination.ts:11:17: 'x' is declared here.
+

tests/baselines/reference/complexRecursiveCollections.types

@@ -1137,7 +1137,7 @@ declare module Immutable {
 >Seq : typeof Seq
 
     function isSeq(maybeSeq: any): maybeSeq is Seq.Indexed<any> | Seq.Keyed<any, any>;
->isSeq : (maybeSeq: any) => maybeSeq is Keyed<any, any> | Indexed<any>
+>isSeq : (maybeSeq: any) => maybeSeq is Indexed<any> | Keyed<any, any>
 >maybeSeq : any
 >Seq : any
 >Seq : any

tests/baselines/reference/conditionalTypes1.errors.txt

@@ -17,8 +17,12 @@ tests/cases/conformance/types/conditional/conditionalTypes1.ts(103,5): error TS2
 tests/cases/conformance/types/conditional/conditionalTypes1.ts(104,5): error TS2322: Type 'Pick<T, { [K in keyof T]: T[K] extends Function ? never : K; }[keyof T]>' is not assignable to type 'T'.
 tests/cases/conformance/types/conditional/conditionalTypes1.ts(106,5): error TS2322: Type 'Pick<T, { [K in keyof T]: T[K] extends Function ? never : K; }[keyof T]>' is not assignable to type 'Pick<T, { [K in keyof T]: T[K] extends Function ? K : never; }[keyof T]>'.
   Type 'T[keyof T] extends Function ? keyof T : never' is not assignable to type 'T[keyof T] extends Function ? never : keyof T'.
+    Type 'keyof T' is not assignable to type 'never'.
+      Type 'string | number | symbol' is not assignable to type 'never'.
+        Type 'string' is not assignable to type 'never'.
 tests/cases/conformance/types/conditional/conditionalTypes1.ts(108,5): error TS2322: Type 'Pick<T, { [K in keyof T]: T[K] extends Function ? K : never; }[keyof T]>' is not assignable to type 'Pick<T, { [K in keyof T]: T[K] extends Function ? never : K; }[keyof T]>'.
   Type 'T[keyof T] extends Function ? never : keyof T' is not assignable to type 'T[keyof T] extends Function ? keyof T : never'.
+    Type 'keyof T' is not assignable to type 'never'.
 tests/cases/conformance/types/conditional/conditionalTypes1.ts(114,5): error TS2322: Type 'keyof T' is not assignable to type 'T[keyof T] extends Function ? keyof T : never'.
   Type 'string | number | symbol' is not assignable to type 'T[keyof T] extends Function ? keyof T : never'.
     Type 'string' is not assignable to type 'T[keyof T] extends Function ? keyof T : never'.
@@ -183,11 +187,15 @@ tests/cases/conformance/types/conditional/conditionalTypes1.ts(288,43): error TS
         ~
 !!! error TS2322: Type 'Pick<T, { [K in keyof T]: T[K] extends Function ? never : K; }[keyof T]>' is not assignable to type 'Pick<T, { [K in keyof T]: T[K] extends Function ? K : never; }[keyof T]>'.
 !!! error TS2322:   Type 'T[keyof T] extends Function ? keyof T : never' is not assignable to type 'T[keyof T] extends Function ? never : keyof T'.
+!!! error TS2322:     Type 'keyof T' is not assignable to type 'never'.
+!!! error TS2322:       Type 'string | number | symbol' is not assignable to type 'never'.
+!!! error TS2322:         Type 'string' is not assignable to type 'never'.
         z = x;
         z = y;  // Error
         ~
 !!! error TS2322: Type 'Pick<T, { [K in keyof T]: T[K] extends Function ? K : never; }[keyof T]>' is not assignable to type 'Pick<T, { [K in keyof T]: T[K] extends Function ? never : K; }[keyof T]>'.
 !!! error TS2322:   Type 'T[keyof T] extends Function ? never : keyof T' is not assignable to type 'T[keyof T] extends Function ? keyof T : never'.
+!!! error TS2322:     Type 'keyof T' is not assignable to type 'never'.
     }
 
     function f8<T>(x: keyof T, y: FunctionPropertyNames<T>, z: NonFunctionPropertyNames<T>) {

tests/baselines/reference/mappedTypeRelationships.errors.txt

@@ -34,7 +34,9 @@ tests/cases/conformance/types/mapped/mappedTypeRelationships.ts(66,5): error TS2
 tests/cases/conformance/types/mapped/mappedTypeRelationships.ts(66,5): error TS2542: Index signature in type 'Readonly<U>' only permits reading.
 tests/cases/conformance/types/mapped/mappedTypeRelationships.ts(72,5): error TS2322: Type 'Partial<T>' is not assignable to type 'T'.
 tests/cases/conformance/types/mapped/mappedTypeRelationships.ts(78,5): error TS2322: Type 'Partial<Thing>' is not assignable to type 'Partial<T>'.
+  Type 'Thing' is not assignable to type 'T'.
 tests/cases/conformance/types/mapped/mappedTypeRelationships.ts(88,5): error TS2322: Type 'Readonly<Thing>' is not assignable to type 'Readonly<T>'.
+  Type 'Thing' is not assignable to type 'T'.
 tests/cases/conformance/types/mapped/mappedTypeRelationships.ts(127,5): error TS2322: Type 'Partial<U>' is not assignable to type 'Identity<U>'.
 tests/cases/conformance/types/mapped/mappedTypeRelationships.ts(143,5): error TS2322: Type '{ [P in keyof T]: T[P]; }' is not assignable to type '{ [P in keyof T]: U[P]; }'.
   Type 'T[P]' is not assignable to type 'U[P]'.
@@ -197,6 +199,7 @@ tests/cases/conformance/types/mapped/mappedTypeRelationships.ts(168,5): error TS
         y = x;  // Error
         ~
 !!! error TS2322: Type 'Partial<Thing>' is not assignable to type 'Partial<T>'.
+!!! error TS2322:   Type 'Thing' is not assignable to type 'T'.
     }
 
     function f40<T>(x: T, y: Readonly<T>) {
@@ -209,6 +212,7 @@ tests/cases/conformance/types/mapped/mappedTypeRelationships.ts(168,5): error TS
         y = x;  // Error
         ~
 !!! error TS2322: Type 'Readonly<Thing>' is not assignable to type 'Readonly<T>'.
+!!! error TS2322:   Type 'Thing' is not assignable to type 'T'.
     }
 
     type Item = {

tests/baselines/reference/mappedTypes5.errors.txt

@@ -1,6 +1,7 @@
 tests/cases/conformance/types/mapped/mappedTypes5.ts(6,9): error TS2322: Type 'Partial<T>' is not assignable to type 'Readonly<T>'.
 tests/cases/conformance/types/mapped/mappedTypes5.ts(8,9): error TS2322: Type 'Partial<Readonly<T>>' is not assignable to type 'Readonly<T>'.
 tests/cases/conformance/types/mapped/mappedTypes5.ts(9,9): error TS2322: Type 'Readonly<Partial<T>>' is not assignable to type 'Readonly<T>'.
+  Type 'Partial<T>' is not assignable to type 'T'.
 
 
 ==== tests/cases/conformance/types/mapped/mappedTypes5.ts (3 errors) ====
@@ -19,6 +20,7 @@ tests/cases/conformance/types/mapped/mappedTypes5.ts(9,9): error TS2322: Type 'R
         let b4: Readonly<T> = rp;  // Error
             ~~
 !!! error TS2322: Type 'Readonly<Partial<T>>' is not assignable to type 'Readonly<T>'.
+!!! error TS2322:   Type 'Partial<T>' is not assignable to type 'T'.
         let c1: Partial<Readonly<T>> = p;
         let c2: Partial<Readonly<T>> = r;
         let c3: Partial<Readonly<T>> = pr;

tests/baselines/reference/recursiveTypeComparison.errors.txt

@@ -0,0 +1,27 @@
+tests/cases/compiler/recursiveTypeComparison.ts(14,5): error TS2322: Type 'Observable<{}>' is not assignable to type 'Property<number>'.
+  Types of property 'needThisOne' are incompatible.
+    Type 'Observable<{}>' is not assignable to type 'Observable<number>'.
+      Type '{}' is not assignable to type 'number'.
+
+
+==== tests/cases/compiler/recursiveTypeComparison.ts (1 errors) ====
+    // Before fix this would take an exceeding long time to complete (#1170)
+
+    interface Observable<T> {
+        // This member can't be of type T, Property<T>, or Observable<anything but T>
+        needThisOne: Observable<T>;
+        // Add more to make it slower
+        expo1: Property<T[]>; //  0.31 seconds in check
+        expo2: Property<T[]>; //  3.11 seconds
+        expo3: Property<T[]>; // 82.28 seconds
+    }
+    interface Property<T> extends Observable<T> { }
+
+    var p: Observable<{}>;
+    var stuck: Property<number> = p;
+        ~~~~~
+!!! error TS2322: Type 'Observable<{}>' is not assignable to type 'Property<number>'.
+!!! error TS2322:   Types of property 'needThisOne' are incompatible.
+!!! error TS2322:     Type 'Observable<{}>' is not assignable to type 'Observable<number>'.
+!!! error TS2322:       Type '{}' is not assignable to type 'number'.
+